Group Policy is available by default on servers with the active directory role (typically domain controllers).
What if you want to control it from another machine however?
The Group Policy Management Console can be added to your windows 2008 server from Server Manager where it is a 'feature' (everything is either a 'role' or a 'feature' nowadays).
To install >
1) Launch Server Manger
2) In the Features pane, click 'Add Features'
3) Select 'Group Policy Management' followed by 'Install'
4) Run gpmc.msc to launch Group Policy Management Console or navigate to it in Server Manager.